Fibre optic probes for spectroscopy are generally known in the art. In general such fibre optic probe comprises a first fibre or a first bundle of fibres to guide light from the proximal end of the probe to the distal end of the probe, and a second fiber or second bundle of fibers are used to guidelight back to the proximal end of the probe. An optical sensor element such as attenuated total reflectance sensor element or transmission/reflection (Trans-Reflex) element is arranged at the distal end of the fibre probe. The optical sensor element generally is arranged and adapted in a way that it interacts with a sample for determining the sample's spectroscopic properties so that light entering the optical sensor element is modified by the sample and is reflected back into the optical fibre of the bundle of optical fibres so it eventually is emitted out of the proximal end of the fibre or the bundle of fibres so they can be analyzed by an analyzing detector element such as spectrometer based on diffraction grating, Fourier Transform interferometer or spectral filter with a related photo element or array of detectors.
Examples for such probe are disclosed in U.S. Pat. No. 5,754,722.